JPS5924192Y2 - Tuning accuracy setting device for automatic tuning circuit - Google Patents

Description

[Detailed description of the invention] The present invention relates to an automatic tuning circuit in a radio broadcast receiver, and in particular improves the accuracy of automatic tuning during automatic tuning, and makes the sensitivity during automatic tuning equal to the sensitivity of the receiver. This invention relates to an accuracy setting device for automatic channel selection that can be set separately.

Generally, an automatic channel selection circuit of a radio broadcast receiver includes a control circuit for adjusting and controlling variable circuit constants of a tuning circuit.

This control circuit fixes the variable circuit constant of the tuning circuit and automatically selects a channel when the receiver receives a broadcast reception signal generated when the receiver receives a radio broadcast signal.

Note that the control circuit outputs a command signal for continuously changing the variable circuit constant until it receives a broadcast reception signal, and hereinafter this state will be referred to as automatic channel selection.

In conventional devices, the accuracy and sensitivity of automatic channel selection are determined by the magnitude of the AGC (automatic gain control) voltage, and have a correlation with the sensitivity of the receiver.

In other words, the sensitivity of the receiver and the AGC voltage generally have an inversely proportional relationship. For example, when the receiver is not receiving any broadcasts and there is no signal, that is, automatic tuning, the sensitivity of the receiver is at its maximum. It is.

In such a case, the AGC voltage is at its minimum, and when a radio broadcast signal is received, a large AGC signal is suddenly generated.
Since a transient phenomenon occurs in the AGC voltage, the accuracy of automatic channel selection is reduced.

In other words, the time from when the receiver receives a radio broadcast signal to when the variable circuit constant is fixed, that is, the time from when the transient phenomenon settles to a steady state until the tuning is completed becomes longer, making it difficult to tune the channel within the desired time. It may not be possible to complete the process, and accurate setting of the variable circuit constants may not be performed.

An object of the present invention is to relate to a tuning accuracy setting device that increases the accuracy of automatic tuning during automatic tuning and allows setting a predetermined automatic tuning sensitivity independently of the sensitivity of a receiver.

The gist of the present invention is that it is attached to a radio broadcast receiver having an automatic tuning circuit, and the AGC voltage terminal that receives the AGC voltage from the receiver is different from the AGC voltage when there is no signal from the receiver. A voltage source capable of supplying a predetermined DC voltage, and a high frequency and intermediate frequency amplifier of the receiver.
an output terminal that is electrically connected to the GC controlled section; a gate signal terminal that receives a gate signal from the receiver indicating that the receiver is not receiving a broadcast signal; and usually the AGC The voltage terminal and the output terminal are electrically connected, and while receiving the gate signal from the gate signal terminal, the voltage source and the output terminal are electrically connected instead of the AGC voltage terminal. A tuning accuracy setting device for an automatic tuning circuit includes a switching element for connection.

Hereinafter, the present invention will be described based on embodiments with reference to the drawings.

FIG. 1 is a schematic block circuit diagram showing an embodiment in which the tuning accuracy setting device according to the present invention is applied to a radio broadcast receiver equipped with an automatic tuning circuit, and FIG. FIG. 2 is a circuit diagram showing an example.

In FIG. 1, a radio broadcast receiver 2 includes an antenna 4,
Tuning circuit 6, high frequency and intermediate frequency amplifier 8, audio amplifier 1
0, a speaker 12, and a control circuit 14.

When power is supplied to the receiver 2, the control circuit 14
When there is no signal, a command signal is issued to the drive mechanism (not shown) of the tuning circuit 6 to continuously change the variable circuit constant, and when a broadcast reception signal is received, the tuning circuit 6 is activated. A command signal is issued to the drive mechanism of the circuit to stop the drive.

As described above, the present invention is characterized in that it can improve the accuracy in determining that the receiver 2 has received a radio broadcast signal, that is, the accuracy in automatic tuning.

To this end, in the present invention, instead of conventionally performing automatic tuning by supplying the AGC voltage to the high frequency/intermediate frequency amplifier 8 during automatic tuning, a DC voltage of a predetermined level is supplied from the voltage source 18. It is configured to supply

In the embodiment shown in FIG. 1, conventionally, in order to prevent unnecessary sounds from being emitted from the speaker when there is no signal, a noise canceling signal 20 that is not output from the control circuit 14 is added to the accuracy setting device or the electronic switch 16. There is.

As is clear from the figure, the desired tuning accuracy and sensitivity set by the voltage source 18 are obtained when there is no signal, that is, during automatic tuning, while after tuning is completed, the AGC voltage increases as usual at high frequency and intermediate frequency. It is added to the width container 8.

Next, referring to FIG. 2, a preferred embodiment of the tuning accuracy setting device 16 according to the present invention will be described.

In the figure, the tuning accuracy setter 16 is electrically connected to the high frequency and intermediate frequency amplifier 8 via an output terminal 40, and an AGC voltage terminal 2 for receiving the AGC voltage.
2. A predetermined drive voltage is applied to the first
A B power supply terminal 26 is provided to supply the base of the transistor 24, and a gate signal terminal 28 is provided to receive a gate signal (in this embodiment, a noise canceling signal) indicating a no-signal state.

In this embodiment, as the voltage source 18, the noise canceling signal voltage can be divided at any ratio using a variable resistor 30, which is connected to the polarity shown in the figure. , the high frequency and intermediate frequency amplifier 8 via a diode 32 that constitutes a switching element to prevent the AGC voltage from flowing backwards after tuning is completed.
It is connected to the.

Further, the noise canceling signal (gate signal) is transmitted via the resistor 34 to the second transistor 36 constituting the switching element.
applied to the base of

The collector of this second transistor 36 is connected to the base of the first transistor 24.

Next, the operation of the tuning accuracy setter 16 will be explained.

First, it is assumed that the receiver 2 is not receiving a broadcast signal and automatic channel selection is being performed.

In this case, a noise canceling signal is applied to the gate signal terminal 28 from the control circuit 14, which drives the second transistor 36 to pass the voltage signal from the B power supply terminal 26 through the second transistor 26. The first transistor 24 is grounded, and the first transistor 24 is rendered non-conductive.

Therefore, the AGC voltage is cut off during automatic tuning.

On the other hand, the noise canceling signal is applied to a variable resistor 30, where it is divided into desired levels and applied to the high frequency/intermediate frequency amplifier 8 to provide a desired automatic tuning sensitivity.

Then, when the driving mechanism of the tuning circuit operates, the tuning frequency is swept, and a broadcast reception signal of a predetermined level is applied to the control circuit 14, the driving mechanism of the tuning circuit 6 is stopped, and the variable circuit constant is fixed and selected. The station is about to be completed.

At the same time, the gate signal, that is, the noise canceling signal disappears, so the voltage from the B power supply terminal 26 is applied to the base of the first transistor 24 via the resistor 38, which becomes conductive and the AGC voltage becomes high frequency as usual. , are supplied to the intermediate frequency amplifier 8.

Here, since the DC voltage of a predetermined level from the voltage source 18 is applied to the high frequency/intermediate frequency amplifier 8, there is no large voltage change at the output terminal 40 even if the AGC voltage is applied.
No transient phenomena occur in the GC voltage.

Therefore, automatic channel selection is completed quickly and reliably.

As explained above, according to the automatic tuning circuit equipped with the tuning accuracy setting device according to the present invention, it is possible to suitably set the tuning sensitivity separately from the sensitivity of the receiver during automatic tuning, and it is possible to set the tuning sensitivity separately from the receiver sensitivity during automatic tuning. Automatic tuning can be performed reliably because the tuning accuracy can be improved compared to the conventional system.

[Brief explanation of drawings]

FIG. 1 is a schematic block circuit diagram showing a preferred example of application of the tuning accuracy setter of the present invention. FIG. 2 is a circuit diagram showing the tuning accuracy setting device according to the present invention. 2 Radio broadcast receiver, 6: Tuning circuit, 8: High frequency, intermediate frequency amplifier, 14: Control circuit, 16: Tuning accuracy setting device, 18: Voltage source, 22: AGC voltage terminal, 24, 32.
36 Niswitching element, 26: B power supply terminal, 28:
Gate signal terminal, 30: variable resistor, 40: output terminal.

Claims (1)

[Claim for Utility Model Registration] A device attached to a radio broadcasting receiver having an automatic channel selection circuit, comprising: an AGC voltage terminal that receives an AGC voltage from the receiver; and an AGC voltage terminal when there is no signal from the receiver. a voltage source that supplies a predetermined DC voltage different from that of the receiver, an output terminal electrically connected to an AGC controlled section of a high frequency and intermediate frequency amplifier of the receiver, and a receiver that receives a broadcast signal; A gate signal terminal that receives a gate signal from the receiver indicating that the AGC is in a non-operating state is normally electrically connected to the AGC voltage terminal and the output terminal. A tuning accuracy setter for an automatic tuning circuit, comprising a switching element for electrically connecting the voltage source and the output terminal instead of the AGC voltage terminal while receiving a signal.